1. Field of the Invention
The present invention relates to an organic electroluminescence (hereinafter referred to as EL) panel and a method of manufacturing the same, and more particularly to an organic EL panel provided with partitions for separating pixels and to a method of manufacturing the partitions.
2. Related Arts
An organic EL panel having such partitions is disclosed in Japanese Unexamined Patent Publications No. Hei 9-102393 and Hei 8-315981. According to the organic EL panel manufacturing method disclosed in these publications, as is shown in FIG. 1A, anodes, transparent electrodes 2 composed of indium tin oxide (hereinafter referred to as ITO), are formed as stripes on a transparent substrate 1, and to separate the pixels, photolithography is used to form electrical insulating partitions 31 that cross and that are perpendicular relative to the transparent electrodes 2. The lower portions of these partitions 31 are tapered invertedly, and their upper portions constitute overhanging portions 310. Then, as is shown in FIG. 1B, using a film deposition mask 37, an organic emission material that emits only one color is deposited on the transparent substrate 1, on which the partitions 31 are formed, at angles indicated by arrows P and Q, so that the organic emission material extends outward to either side and under the overhanging portions 310. This deposition process is repeated for each color to obtain an organic emission layers 32. Thereafter, as is shown in FIG. 1C, to form cathode electrodes 33 on the partitions 31 and the emission layers 32, the film deposition mask 37 is removed and a cathode electrode material is deposited in the direction, as is indicated by arrows S, that is substantially perpendicular to the transparent substrate 1. Since each partition 31 has overhanging portions 310, the cathode electrode 33 on each side of a partition 31 is electrically insulated.
As is shown in FIGS. 1A to 1C, the partitions 31, which are obtained by using a resist to provide an invertedly tapered shape, are employed to separate pixels and cathodes. When a resist is employed, however, the resist's residual developing liquid, an etching liquid and a small quantity of water act together to cause deterioration of the interfaces of the organic emission layer 32 and the cathode electrodes 33. As a result, a non-emission point called a dark spot is generated. The generation of a dark spot makes it difficult to extend the service life of a panel. The overhanging portions 310 of the invertedly tapered partitions 31 are formed by using a difference in the developing speeds that is the result of differences in the light exposure volumes in the direction of thickness. Thus, the sizes of overhanging portions 310 are unstable and insufficient separations tend to occur. When an insufficient separation occurs, not only are a cathode electrode 33 and an anode, transparent electrode 2 short-circuited and a non-emission element generated, but also the panel may be damaged by heat due to the short circuit. In addition, for such a display panel, the partitions 31 must have, at the least, a predetermined width in order to prevent insufficient separation, so that the area required for the partitions 31, which serve as non-light emission portions, is increased. As a result, the aperture ratio can not be increased, and it is difficult to attain a smaller pixel size.